The present invention relates to propylene-based resins and propylene-based polymer compositions, and also to films and laminates made of them.
More precisely, the invention relates to propylene-based polymers and propylene-based polymer compositions, and also to films, for example, those for wrapping or packaging edibles, as well as laminates, fibers, sheets and moldings made of them, and they have the advantages of good low-temperature heat-sealability, well-balanced toughness and heat-sealability which no one has heretofore experienced in the art, as well as improved anti-blocking properties, improved slip characteristics and improved moldability.
Polypropylene has good physical properties, as being tough and resistant to heat, and is inexpensive. Therefore, it is a general-purpose resin having many applications in various fields.
For example, as having the advantages of high transparency, high toughness, good heat resistance and little water absorption, polypropylene is used for cast films such as biaxially-oriented films, laminate films, etc. In particular, films of a crystalline propylene-based polymer are widely used as wrapping or packaging films, as having the advantages of high toughness, high transparency and good moisture-proofness.
In general, the films are formed into bags through heat-sealing. After having been filled with objects, the bags are closed by again heat-sealing their open ends.
The recent tendency in the art is toward high-speed production lines for fabricating bags and packages so as to improve the productivity. To meet the requirement, it is desired to improve the quality of films. For example, a plurality of resins having different properties are layered, and the resulting multi-layered films are being widely used. Of such multi-layered films, the resin film to be the outermost layer is specifically desired to have good physical properties of low-temperature heat-sealability (this is for facilitating high-speed production lines for fabricating bags and packages), slip characteristics (these are for attaining smooth re-winding of films), and anti-blocking properties.
In other fields of sheets and non-woven fabrics except the films as above, it is also desired to lower the temperature for layer lamination.
As compared with ethylene-based polymers, propylene-based polymers may have a larger degree of supercooling necessary for the start of their crystallization, and therefore have a lower crystallization temperature (Tc) when their melting point (Tm) is on the same level as that of ethylene-based polymers. This is more noticeable for propylene-based copolymers and polymers with lower stereospecificity, a shaving lower crystallinity. As a result, propylene-based polymers are often difficult to mold, and, in addition, their resin characteristics are poor. In particular, their transparency is low, the heat-sealing temperature (HST) for them is high, and their elasticity and impact resistance are poor. Especially for film applications, propylene-based polymers are often confronted with many problems. For example, with propylene-based polymers being required to have low-temperature heat-sealability comparable to that of linear low-density polyethylene, the problems are that the polymers often fail to be formed into good films, in particular, the films formed often fail to be smoothly released from chill rolls, the edges of the films are unstable, and the films are readily scratched by sweeper rolls. Therefore, to obtain films, fibers, sheets and moldings of the polymers having good low-temperature heat-sealability, the problems with the polymers as above must be solved.
Heretofore, a method of copolymerizing propylene homopolymers with a small amount a comonomer of ethylene, 1-butene or the like has been proposed for improving the low-temperature heat-sealability of films of the polymers. In the method, however, a large amount of ethylene or 1-butene must be copolymerized with the polymers in order to secure satisfactory low-temperature heat-sealability of the polymers. If so, the polymers shall contain a large amount of sticky side products, and, as a result, their anti-blocking properties are greatly worsened, and, in addition, the side products bleed out of the films of the polymers whereby the films are seen whitish and their appearances are not good. After all, the films of the polymers are not on the practicable level. What is more, the crystallinity of the polymers is low, and the films of the polymers could not be tough. Further, the moldability of the polymers is poor, and the anti-blocking properties of the films of the polymers are poor.
To solve the problem, tried is a method of removing the sticky component from the polymers by dissolving it in an inert solvent. In this method, however, even the low-temperature-melting crystalline component that contributes to the low-temperature heat-sealability of the polymers is inevitably removed from the polymers. At present, after all, the low-temperature heat-sealability of the polymers could not be still improved to a satisfactory degree even in the method.
On the other hand, tried is another method of copolymerizing propylene homopolymers with some xcex1-olefin other than ethylene or 1-butene, for example, with 1-hexene, 1-octene, 4-methyl-1-pentene or the like. According to the prior art technology, however, resins obtained all have an extremely broad compositional distribution, and it is difficult to improve their anti-blocking properties, toughness and moldability up to the practicable level.
Conventional propylene-based polymers obtained in the presence of a known Ziegler catalyst have a broad molecular weight distribution and a broad compositional distribution, and are not homogeneous. Therefore, the high-crystalline component in the polymers could readily form crystalline nuclei, and, as a result, the degree of supercooling necessary for the start of their crystallization is not so large and the moldability of the polymers is not so much lowered. However, as their composition is not homogeneous, the polymers have poor physical properties. In particular, as containing a sticky component and a high-crystalline component, the polymers could not exhibit good physical properties intrinsic to resins.
Recently, single-site metallocene catalysts have been developed. Polypropylene obtained in the presence of such a metallocene catalyst has a homogeneous composition and contains a reduced amount of a sticky component and a high-crystalline component that may worsen the physical properties of the polymer. Therefore, the physical properties of the polymer are better than those of the other polymers produced in the presence of any other conventional catalyst. However, as the polymer has a homogeneous composition, the degree of supercooling for it is enlarged and the moldability of the polymer is lowered.
A method of using the propylene-based polymer obtained in the presence of a metallocene catalyst, as a heat-sealability improver for the propylene-based polymer obtained in the presence of a conventional Ziegler catalyst has been proposed (Japanese Patent Laid-Open Nos. 173016/1990, 112682/1993, 112683/1993). The method is effective in some degree for improving the balance of the heat-sealability and the toughness of the polymer films, but could not still solve the problem with the polymer composition in point of the balance between the moldability of the polymer composition and the physical properties of the polymer films.
In that situation, the present invention is to further improve the heat-sealability of polypropylene films, without interfering with the intrinsic good properties of the films, to such a degree that the improved heat-sealability of the films is comparable to that of linear low-density polyethylene films. Specifically, the object of the invention is to provide propylene-based polymers and propylene-based polymer compositions, and also their films including those for wrapping and packaging edibles, as well as their fibers, sheets, non-woven fabrics and other various moldings all having highly improved and well-balanced physical properties including heat-sealability, anti-blocking properties, toughness and impact resistance.
Another object of the invention is to provide propylene-based resins favorable to sealants, and also to provide films of the resin, as well as laminates comprising at least one layer of the resin.
We, the present inventors have assiduously studied so as to attain the objects noted above, and, as a result, have found that, when a substance capable of readily inducing crystalline nuclei in a melt of a propylene-based polymer to thereby reduce the degree of supercooling necessary for the polymer crystallization but not detracting from the physical properties of the polymer at all, for example, a nucleating agent, a high-molecular nucleating agent, a propylene-based polymer having a low degree of crystallinity, a propylene-based polymer having a low molecular weight or the like is added to a propylene-based polymer obtained in the presence of a metallocene catalyst and having a homogeneous composition, then the resulting propylene-based polymer composition could have well-balanced physical properties and moldability. On the basis of this finding, we have completed the present invention.
Specifically, the invention is summarized as follows:
The first aspect of the invention includes the following:
(1) A propylene-based polymer composition comprising (1-A) a propylene homopolymer obtained through polymerization in the presence of a metallocene catalyst and having an isotactic pentad fraction (mmmm fraction) of from 80 to 99 mol %, a molecular weight distribution (Mw/Mn) of at most 3.5, and an intrinsic viscosity [xcex7] of from 0.5 to 5.0 dl/g, and (1-B) at least 10 ppm of a nucleating agent.
(2) A propylene-based polymer composition comprising (1-A) a propylene-based random copolymer obtained through polymerization of propylene, and ethylene and/or an xcex1-olefin having from 4 to 20 carbon atoms in the presence of a metallocene catalyst, and having a propylene-derived structural unit content of from 80 to 100 mol %, an ethylene and/or C4-20 xcex1-olefin-derived structural unit content of from 0 to 20 mol %, a molecular weight distribution (Mw/Mn) of at most 3.5, and an intrinsic viscosity [xcex7] of from 0.5 to 5.0 dl/g, and (1-B) at least 10 ppm of a nucleating agent, for example, metal salts of organic phosphoric acids, talc, dibenzylidene-sorbitol and its derivatives, or amide compounds, and the like.
(3) A propylene-based polymer composition of which the tensile modulus (TM (MPa)) in the MD direction and the heat-sealing temperature (HST (xc2x0 C.)) satisfy the following formula (1-II):
xe2x80x83TMxe2x89xa722xc3x97HSTxe2x88x921850xe2x80x83xe2x80x83(1-II).
(4) Films as formed by casting the propylene-based polymer composition of any of above (1) to (3).
(5) Films for wrapping or packaging edibles, which are formed by casting the propylene-based polymer composition containing, as the nucleating agent, any of metal salts of organic phosphoric acids or talc.
The second aspect of the invention includes the following:
(6) A polypropylene-based resin composition comprising (2-A) from 50 to 99 parts by weight of a propylene homopolymer obtained through polymerization in the presence of a metallocene catalyst and having an isotactic pentad fraction (mmmm fraction) of from 80 to 99 mol %, an intrinsic viscosity [xcex7] of from 1.0 to 2.0 dl/g, and a molecular weight distribution (Mw/Mn) of at most 3.5, and (2-B) from 1 to 50 parts by weight of a propylene homopolymer obtained through polymerization in the presence of a metallocene catalyst and having an intrinsic viscosity [xcex7] of from 0.01 to 1.0 dl/g, and a molecular weight distribution (Mw/Mn) of at most 3.5; and films made of the polypropylene-based resin composition.
The third aspect of the invention includes the following:
(7) A propylene-based resin comprising (3-A) from 55 to 99 parts by weight of a copolymer of propylene and an xcex1-olefin having at least 5 carbon atoms, and (3-B) from 1 to 45 parts by weight of a propylene-based polymer of which the crystallization temperature as measured through differential scanning calorimetry is higher than that of (3-A).
(8) The propylene-based resin of (7), wherein the crystallization temperature (Tca (xc2x0 C.)) of the copolymer (3-A) and the crystallization temperature (Tcb (xc2x0 C.)) of the propylene-based polymer (3-B), both measured through differential scanning calorimetry, satisfy the following formula:
Tcbxe2x88x92Tcaxe2x89xa720xe2x80x83xe2x80x83(3-I).
(9) The propylene-based resin of (7) or (8), which satisfies the following requirements (i), (ii) and (iii) in its temperature-programmed fractionation chromatography (TREF):
(i) The amount of its fraction eluted within the temperature range between (Tpxe2x88x925)xc2x0 C. and (Tp+5)xc2x0 C. is at least 65% by weight, with Tp being the peak temperature for essential elution;
(ii) The amount of its fraction eluted within the temperature range not higher than 0xc2x0 C. is at most 3% by weight; and
(iii) The amount of its fraction eluted within the temperature range not lower than Tp+10xc2x0 C. is from 1 to 45% by weight of all eluates.
(10) The propylene-based resin of any of (7) to (9), of which the peak top temperature on the highest temperature side in its crystallization curve measured through differential scanning calorimetry is not lower than 85xc2x0 C.
(11) The propylene-based resin of any of (7) to (19), of which the peak top temperature on the lowest temperature side in its melting curve measured through differential scanning calorimetry is not higher than 150xc2x0 C.
(12) The propylene-based resin of any of (7) to (11), wherein the copolymer (A) satisfies the following (A-i) and (A-ii) in its temperature-programmed fractionation chromatography:
(A-i) The amount of its fraction eluted within the temperature range between (Tpxe2x88x925)xc2x0 C. and (Tp+5)xc2x0 C. is at least 70% by weight, with Tp being the peak temperature for essential elution; and
(A-ii) The amount of its fraction eluted within the temperature range not higher than 0xc2x0 C. is at most 3% by weight.
(13) The propylene-based resin of any of (7) to (12), wherein the copolymer (3-A) satisfies at least any one of the following (A-iii), (A-iv) and (A-v):
(A-iii) The content of xcex1-olefin units having at least 5 carbon atoms (xcex1 mol %) in the copolymer (3-A) is from 0.1 mol % to 12 mol %;
(A-iv) The stereospecificity index (P) of the copolymer (3-A) is at least 85 mol %; and
(A-v) The intrinsic viscosity ([xcex7]) of the copolymer (3-A), as measured in decalin at 135xc2x0 C., is from 0.5 to 3.0 g/dl.
(14) The propylene-based resin of any of (7) to (12), wherein the constituent xcex1-olefin units having at least 5 carbon atoms in the copolymer (3-A) are from at least one of 1-octene, 1-dodecene and 1-decene.
(15) Films made of the propylene-based resin of any of (7) to (14); or laminates comprising at least one layer of the propylene-based resin.
The fourth aspect of the invention includes the following:
(16) A propylene-based random copolymer of propylene and an xcex1-olefin having at least 5 carbon atoms, which satisfies the following formula (4-I):
Tmxe2x89xa6140, and Tmxe2x89xa6160xe2x88x927xcex1xe2x80x83xe2x80x83(4-I)
wherein Tm (xc2x0 C.) indicates the melting point of the copolymer measured through differential scanning calorimetry, and xcex1 (mol %) indicates the content of xcex1-olefin units having at least 5 carbon atoms in the copolymer;
and satisfies the following formula (4-II):
Tcxe2x89xa70.75Tmxe2x88x9215xe2x80x83xe2x80x83(4-II)
wherein Tc (xc2x0 C.) and Tm (xc2x0 C.) each indicate the crystallization temperature and the melting point, copolymer both measured through differential scanning calorimetry.
(17) A propylene-based random copolymer composition comprising (4-A) a propylene-based random copolymer of propylene and an xcex1-olefin having at least 5 carbon atoms, and (4-B) a substance having the capability of nucleation, the composition satisfying the following formula (4-I):
Tmxe2x89xa6140, and Tmxe2x89xa6160xe2x88x927xcex1xe2x80x83xe2x80x83(4-I)
wherein Tm (xc2x0 C.) indicates the melting point of the composition measured through differential scanning calorimetry, and xcex1 (mol %) indicates the content of xcex1-olefin units having at least 5 carbon atoms in the composition;
and satisfying the following formula (4-II):
Tcxe2x89xa70.75Tmxe2x88x9215xe2x80x83xe2x80x83(4-II)
wherein Tc (xc2x0 C.) and Tm (xc2x0 C.) each indicate the crystallization temperature and the melting point, respectively, of the composition both measured through differential scanning calorimetry.
(18) The propylene-based random copolymer of above (16), or the propylene-based random copolymer composition of (17), wherein the content of xcex1-olefin units having at least 5 carbon atoms is from 0.1 to 12 mol %.
(19) The propylene-based random copolymer of above (16) or (18), which has a stereospecificity index (P) of at least 85 mol %; or the propylene-based random copolymer composition of (17) or (18), wherein the copolymer has a stereospecificity index (P) of at least 85 mol %.
(20) The propylene-based random copolymer of above (16), (18) or (19), or the propylene-based random copolymer composition of any of (17) to (19), which has an intrinsic viscosity [xcex7], as measured in decalin at 135xc2x0 C., of from 0.5 to 3 dl/g.
(21) The propylene-based random copolymer of above (16), or any of (18) to (20), or the propylene-based random copolymer composition of any of (17) to (20), wherein the xcex1-olefin units having at least 5 carbon atoms are from at least one of 1-octene, 1-decene and 1-dodecene.
(22) Films made of the copolymer or the copolymer composition of any of above (16) to (21); laminates comprising at least one layer of the copolymer or the copolymer composition; as well as fibers, sheets or moldings comprising the copolymer or the copolymer composition.
The fifth aspect of the invention includes the following:
(23) A propylene-based random copolymer of propylene and 1-butene, which satisfies the following formula (5-I):
Tmxe2x89xa6160xe2x88x923xcex1xe2x80x83xe2x80x83(5-I)
wherein Tm (xc2x0 C.) indicates the melting point of the copolymer measured through differential scanning calorimetry, and xcex1 (mol %) indicates the 1-butene unit content of the copolymer;
and satisfies the following formula (5-II):
Tcxe2x89xa70.75Tmxe2x88x9210xe2x80x83xe2x80x83(5-II)
wherein Tc (xc2x0 C.) and Tm (xc2x0 C.) each indicate the crystallization temperature and the melting point, respectively, of the copolymer both measured through differential scanning calorimetry.
(24) A propylene-based random copolymer composition comprising (5-A) a propylene-based random copolymer of propylene and 1-butene, and (5-B) a substance having the capability of nucleation, the composition satisfying the following formula (5-I):
Tmxe2x89xa6160xe2x88x923xcex1xe2x80x83xe2x80x83(5-I)
wherein Tm (xc2x0 C.) indicates the melting point of the composition measured through differential scanning calorimetry, and xcex1 (mol %) indicates the 1-butene content of the composition;
and satisfying the following formula (5-II):
Tcxe2x89xa70.75Tmxe2x88x9210xe2x80x83xe2x80x83(5-II)
wherein Tc (xc2x0 C.) and Tm (xc2x0 C.) each indicate the crystallization temperature and the melting point, respectively, of the composition both measured through differential scanning calorimetry.
(25) The propylene-based random copolymer of above (23), or the propylene-based random copolymer composition of (24), which has a 1-butene content of from 0.1 to 30 mol %.
(26) The propylene-based random copolymer of above (23) or (25), which has a stereospecificity index (P) of at least 85 mol %; or the propylene-based random copolymer composition of (24) or (25), wherein the copolymer has a stereospecificity index (P) of at least 85 mol %.
(27) The propylene-based random copolymer of above (23), (25) or (26), or the propylene-based random copolymer composition of any of (24) to (26), which has an intrinsic viscosity [xcex7], as measured in decalin at 135xc2x0 C., of from 0.5 to 3 dl/g.
(28) Films made of the copolymer or the copolymer composition of any of above (23) to (27); laminates comprising at least one layer of the copolymer or the copolymer composition; and fibers, sheets or moldings comprising the copolymer or the copolymer composition.
The sixth aspect of the invention includes the following:
(29) A propylene-based polymer composition comprising (A) a propylene-based random copolymer obtained through polymerization of propylene and an xcex1-olefin having at least 4 carbon atoms in the presence of a metallocene catalyst, and having a propylene-derived structural unit content of from 80 to 99.9 mol %, an xcex1-olefin-derived structural unit content of from 0.1 to 20 mol %, and an intrinsic viscosity [xcex7] of from 0.5 to 5.0 dl/g, and (B) at least 10 ppm of a nucleating agent.
(30) The propylene-based polymer composition of above (29), wherein the xcex1-olefin has at least 5 carbon atoms.
(31) The propylene-based polymer composition of above (29), in which the xcex1-olefin is 1-butene and of which the tensile modulus (TM (MPa)) in the MD direction and the heat-sealing temperature (HST (xc2x0 C.)) satisfy the following formula (6-I):
TMxe2x89xa722xc3x97HSTxe2x88x921850xe2x80x83xe2x80x83(6-I).
(32) The propylene-based polymer composition of above (29), of which the tensile modulus (TM (MPa)) in the MD direction and the heat-sealing temperature (HST (xc2x0 C.)) satisfy the following formula (6-II):
TMxe2x89xa722xc3x97HSTxe2x88x921700xe2x80x83xe2x80x83(6-II).
(33) The propylene-based polymer composition of above (29), of which the boiling diethyl ether-soluble content (E (% by weight)) and the xcex1-olefin content (xcex1 (mol %)) satisfy the following formula (6-III):
Exe2x89xa60.2xc3x97xcex1+1.0xe2x80x83xe2x80x83(6-III).
(34) Films as formed by casting the propylene-based polymer composition of any of above (29) to (33).